Method for preventing interference of contactless card reader and touch functions when they are physically and logically bound together for improved authentication security

ABSTRACT

A system for physically and logically integrating near field communication technology, touch sensor technology and display technology by using a more powerful near field communication antenna disposed under the touch sensor and display screen for transmitting, and a smaller near field communication antenna on top of the touch sensor for receiving near field communication signals.

CROSS REFERENCE TO RELATED APPLICATIONS

This document claims priority to and incorporates by reference all ofthe subject matter included in the provisional patent application docketNo. 5093.CIRQ.PR, having application No. 61/579,846, filed Dec. 23,2011.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates generally to touch sensors, near fieldcommunication technology such as NFC technology that is found incontactless smart cards, and a display. More specifically, the presentinvention physically and logically combines near field communicationtechnology, touch sensor technology and display technology by using amore powerful near field communication antenna disposed under or arounda perimeter of the touch sensor and display screen for transmitting, anda smaller near field communication antenna under or on top of the touchsensor for receiving near field communication signals. The system mayalso enable the shared use of certain components for the purposes ofeach of these functions, thereby offering increased security from attackby more closely integrating the physical and logical operations whileoffering simultaneous and independent operation of each.

Description of the Related Art

There are several designs for capacitance sensitive touchpads. It isuseful to examine the underlying technology to better understand how anycapacitance sensitive touchpad can be modified to work with the presentinvention.

The CIRQUE® Corporation touchpad is a mutual capacitance-sensing deviceand an example is illustrated as a block diagram in FIG. 1. In thistouchpad 10, a grid of X (12) and Y (14) electrodes and a senseelectrode 16 is used to define the touch-sensitive area 18 of thetouchpad. Typically, the touchpad 10 is a rectangular grid ofapproximately 16 by 12 electrodes, or 8 by 6 electrodes when there arespace constraints. Interlaced with these X (12) and Y (14) (or row andcolumn) electrodes is a single sense electrode 16. All positionmeasurements are made through the sense electrode 16.

The CIRQUE® Corporation touchpad 10 measures an imbalance in electricalcharge on the sense line 16. When no pointing object is on or inproximity to the touchpad 10, the touchpad circuitry 20 is in a balancedstate, and there is no charge imbalance on the sense line 16. When apointing object creates imbalance because of capacitive coupling whenthe object approaches or touches a touch surface (the sensing area 18 ofthe touchpad 10), a change in capacitance occurs on the electrodes 12,14. What is measured is the change in capacitance, but not the absolutecapacitance value on the electrodes 12, 14. The touchpad 10 determinesthe change in capacitance by measuring the amount of charge that must beinjected onto the sense line 16 to reestablish or regain balance ofcharge on the sense line.

The system above is utilized to determine the position of a finger on orin proximity to a touchpad 10 as follows. This example describes rowelectrodes 12, and is repeated in the same manner for the columnelectrodes 14. The values obtained from the row and column electrodemeasurements determine an intersection which is the centroid of thepointing object on or in proximity to the touchpad 10.

In the first step, a first set of row electrodes 12 are driven with afirst signal from P, N generator 22, and a different but adjacent secondset of row electrodes are driven with a second signal from the P, Ngenerator. The touchpad circuitry 20 obtains a value from the sense line16 using a mutual capacitance measuring device 26 that indicates whichrow electrode is closest to the pointing object. However, the touchpadcircuitry 20 under the control of some microcontroller 28 cannot yetdetermine on which side of the row electrode the pointing object islocated, nor can the touchpad circuitry 20 determine just how far thepointing object is located away from the electrode. Thus, the systemshifts by one electrode the group of electrodes 12 to be driven. Inother words, the electrode on one side of the group is added, while theelectrode on the opposite side of the group is no longer driven. The newgroup is then driven by the P, N generator 22 and a second measurementof the sense line 16 is taken.

From these two measurements, it is possible to determine on which sideof the row electrode the pointing object is located, and how far away.Using an equation that compares the magnitude of the two signalsmeasured then performs pointing object position determination.

The sensitivity or resolution of the CIRQUE® Corporation touchpad ismuch higher than the 16 by 12 grid of row and column electrodes implies.The resolution is typically on the order of 960 counts per inch, orgreater. The exact resolution is determined by the sensitivity of thecomponents, the spacing between the electrodes 12, 14 on the same rowsand columns, and other factors that are not material to the presentinvention.

The process above is repeated for the Y or column electrodes 14 using aP, N generator 24

Although the CIRQUE® touchpad described above uses a grid of X and Yelectrodes 12, 14 and a separate and single sense electrode 16, thesense electrode can actually be the X or Y electrodes 12, 14 by usingmultiplexing.

Previously patented technology describes two-factor or three-factor userauthentication methods such as described in U.S. Pat. No. 7,306,144 (the144 patent), wherein using a debit ATM card or accessing protectedinformation or a secure location, it is often desirable to integrate thefunction of verifying the identity of the user. Verifying identity usinga two-factor system may be accomplished using (1) something the userhas, such as an account number and one time password generated inside ofa contactless card or cell phone, and (2) something that only the userknows, such as a secret PIN/password. Verifying using a three-factorsystem provides an additional layer of security by adding (3) some userbiometric such as a user's fingerprint.

Responding to this desire, the 144 patent was obtained which integrateda contactless card reader touch screen and the biometric contactlesstouchpad to provide the ability to the payment industry to createapplications such as near field communication (NFC) enabled touch screenPIN entry devices and NFC enabled laptop computers for the networkingindustry. These devices may be used to create secure VPN login devicesto give access to remote business networks, and for the physicalsecurity industry to create secure token entry devices, such as forbuilding access. The NFC capabilities include contactless card readerfunctions that enable the reading of data on a smart card, smart phoneor other device that may store data that can be read using wirelesscommunication such as through NFC.

In the 144 patent, the integrated contactless card reader is integratedinto the hardware of a touchpad, wherein the circuit board substrate ofthe touchpad provides a mechanical substrate on which the hardware ofthe contactless card reader can be disposed, and wherein the touchpad isalready widely distributed in other electronic appliances and as astand-alone device.

The 144 patent describes “a contactless smart card reader that isintegrated into the hardware of a touchpad, wherein the circuit boardsubstrate of the touchpad provides a mechanical substrate on which thehardware of the contactless smart card reader can be disposed, andwherein the touchpad is already widely distributed in other electronicappliances, and as a stand-alone device. . . . Such electronicappliances that incorporate a touchpad include many portable electronicappliances such as laptop computers, personal digital assistants (PDAs),mobile telephones, digital cameras, digital camcorders, etc.” . . . TheCirque® GLIDEPOINT® technology is also integrated into devices that arenot designed to be mobile, such as point-of-sale input devices. Forexample, when a user provides a credit card or a debit card to a cashierfor a purchase, it is common to see a dumb card reader that enables thecredit or debit card to be swiped in order to read a magnetic strip. Theuser then typically uses a pen that is coupled to the dumb card readerand either enters a signature or a debit card number. Thus, the CIRQUE®GLIDEPOINT® technology is capable of receiving diverse forms of userinput.”

An example of an integrated contactless touchpad is constructed byplacing a wire loop antenna or copper traces around the touch sensor.The drawback to this design is that many of the physical structures ofthe touchpad sensors and the contactless card reader interferemechanically with each other, as well as electrically.

In an example of a mechanical problem, the touchpad sensor is often toolarge to support placement of an appropriately sized contactless cardreader antenna due to constraints of the standards for contactless cardreader operative volume, thereby limiting the practical size of anintegrated system.

In an example of an interference problem, the strong magnetic fieldnecessary to power the contactless card reader creates strong eddycurrents within the touchpad sensor, thereby causing operation outsideof specifications, and malfunctions or inoperability is the result.

In a related interference problem, the touchpad creates strongelectrostatic fields that are necessary to detect a finger. These strongfields often cause the contactless card reader to have insufficientsignal integrity.

The adverse effects of both the electrostatic fields and magneticinterference is often a result of 1) the contactless card reader signalcausing non-linear effects due to noise/interference signal levels beinglarge enough to trigger ESD diodes in touchpad circuitry, 2) difficultyfor the touchpad front-end electronics or analog-to-digital converters(ADCs) in tracking the interference also causing non-linear effects anderror in measurement, and 3) the amplitude modulation frequency of NFCis often very close to the touch sensing stimulus frequency, therebycreating in-band ground bounce.

Accordingly, what is needed are new techniques for physically combiningthe area of operation of NFC technology and a touch sensor that willenable integration of an appropriately sized NFC antenna near the touchsensor that accommodates the physical interference of components,especially when using different materials such as ITO and copper traces.

It would be a further advantage to dispose the circuitry of thesesystems near enough to each other to prevent eavesdropping or tappinginto the signals between them to thereby provide an integrated systemthat is more secure than existing integrated systems. It would be anadvantage to provide new techniques that will remove the electrical andmagnetic interaction between the two systems of a contactless cardreader and a touchpad. It would also be of benefit to integrate theelectronics into a single package to address the very limited space ofthe touchpad and associated routing space typical of today's small andportable electronic appliances. It is also important to control anoperating or active volume because of limitations of standards thatcontrol operation of an NFC antenna.

BRIEF SUMMARY OF THE INVENTION

In a preferred embodiment, the present invention is a system forphysically and logically integrating near field communicationtechnology, touch sensor technology and display technology by using amore powerful near field communication antenna disposed under or arounda perimeter of the touch sensor and display screen for transmitting, anda smaller near field communication antenna that is under or on top ofthe touch sensor for receiving near field communication signals, whereinthe system may also enable the shared use of certain components for thefunctions of the touch sensor technology, near field communicationtechnology and display technology, wherein the integrated systems aremade more secure from attack by bringing physical components closertogether and shielding them from physical probes, and wherein thefunctions are performed within the integrated system such thatauthentication is performed entirely within a secured area, therebyprotecting a transaction from outside manipulation or exposure.

It is a first object that the touch sensor, NFC and display functionscan be physically performed simultaneously and/or independently fromeach other.

It is a second object that the form factor of the integrated system canbe as small as a stand-alone touch sensor having an integrated NFCdevice used for contactless card communication, and as large as akeyless entry system.

It is a third object that the form factor of an integrated systemincludes a touchscreen as the touch sensor and a contactless card readerthat is as small as a PIN entry device and as large as an ATM or otherautomated financial transaction device.

These and other objects, features, advantages and alternative aspects ofthe present invention will become apparent to those skilled in the artfrom a consideration of the following detailed description taken incombination with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a block diagram of the components of a capacitance-sensitivetouchpad as made by CIRQUE® Corporation and which can be operated inaccordance with the principles of the present invention.

FIG. 2A is a cut-away profile view of a first embodiment of the presentinvention showing two separate NFC antennas, a large one fortransmitting and a smaller one for receiving NFC signals.

FIG. 2B is a cut-away profile view of an alternative embodiment of thepresent invention showing a different stack-up arrangement of thesmaller NFC antenna.

FIG. 3 is a cut-away profile view of an alternative embodiment where aplurality of receiving NFC antennas are shown.

FIG. 4 is a cut-away profile view showing the touch sensor and thesecond NFC antenna sharing electrodes.

FIG. 5 is a cut-away profile view showing the touch sensor and thedisplay screen sharing electrodes.

FIG. 6 is a cut-away profile view showing the touch sensor, the displayscreen and the second NFC antenna 46 sharing electrodes.

FIG. 7 is a top view of a first embodiment showing cuts in two layers ofa ground plane that illustrates the concepts of the present invention

FIG. 8 is a top view of an alternative embodiment to the ground plane ofFIG. 7.

FIG. 9 is a ground plane implemented on the same substrate as an NFCantenna.

FIG. 10 is a stack-up comprised of a touch sensor, a display screen, andan NFC antenna that is for both transmitting and receiving.

FIG. 11 shows that at least one substrate 70 may be disposed between thetouch sensor and the second NFC antenna.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made to the drawings in which the various elementsof the present invention will be given numerical designations and inwhich the invention will be discussed so as to enable one skilled in theart to make and use the invention. It is to be understood that thefollowing description is only exemplary of the principles of the presentinvention, and should not be viewed as narrowing the claims whichfollow.

The use of the term “touch sensor” should be considered asinterchangeable with the terms “touch sensing device”, “touchpad”,“touch screen”, touch panel” and “touch sensitive device” and othersimilar touch devices. Likewise, the term “near field communicationantenna” should be considered as interchangeable with the terms“contactless card reader”, “RFID reader” and “blue tooth antenna”.Furthermore, the “system” referred to may include any combination of twoor all three components comprised of a touch sensor, a near fieldcommunication antenna and a display, using all of the interchangeableterms. Accordingly, some embodiments are directed to touch screens thatcombine all three components, and some are directed to touchpads havingNFC technology, with no display directly associated with the touchsensor itself.

The present invention may be implemented in various embodiments toaddress the different problems that are solved by the present invention.The problems that are addressed by these embodiments should beconsidered to include but not be limited to the system of touch sensor,NFC and display technology 1) where the components may interfere witheach other, 2) preventing eavesdropping or intrusion into the system, 3)using too much space for an integrated system, and 4) needing to controlan operating volume in accordance with standards for operating NFCtechnology.

In the prior art, integration of NFC, display and touch sensingtechnology usually includes placement of an NFC antenna around the touchsensor and the use of separate modules, communication capabilities andpower cables resulting in increased size and complexity of an integratedsystem. It is therefore desirable to reuse or have shared use ofcomponents that can be used by more than one device.

In payment applications such as when using POS PIN entry devices, it isdesirable to make the system secure from physical attack and yet providea secure connection to the host. This may be implemented using theembodiments of the present invention.

In the embodiments of the present invention, NFC functions include butshould not be considered limited to wireless communication functionssuch as using a contactless card reader for communication with a smartcard, or reading a smart card at keyless entry system, or any otherfunction that requires NFC technology, a display and a touch function.

Because an NFC enabled touch sensor is generally used in securityrelated applications, it is a substantial improvement over the prior artto both physically and logically combine touch, display andcommunication functions into a single physically secure device.Accordingly, the present invention provides improved integration andsecurity by combining NFC, display and touch sensor technology, or atleast two of the three functions, into a single chip package, or in atamper resistant security module or secure cryptographic device capableof withstanding an attacker attempting to eavesdrop or probeauthentication activity.

While it may be novel to so closely integrate two or three form-factorauthentication functions in a tamper resistant package or module, thereare problems unique to close integration of NFC, display and touchtechnologies that have to be overcome in order to make the integratedsystem function as desired.

For example, consider the need for authentication of a financialtransaction. In a two form-factor process, the first form factor is theentry of information that is supposedly known only to the user. Thisinformation is typically in the form of a personal identification number(PIN), and can be entered on a touch sensor. The second form factor isthe use of a token in combination with a transaction authorizationnumber (TAN). The TAN represents a one-time password to authenticatetransactions. TANs can be distributed in different ways. The most secureway of using TANs is to generate them by need using a security token.These token generated TANs depend on the time and a unique secret,stored in the security token. Usually online banking with PIN/TAN isdone via a web browser using SSL secured connections, so that there isno additional encryption needed.

By placing the circuitry for a touch sensor in very close proximity tothe circuitry for NFC, it is possible to protect the communication thatmust take place between these systems in order to performauthentication. Security may be achieved in two ways. By physicallymaking the systems close, they can operate without having to communicateusing physically accessible lines of communication. By logicallyintegrating the systems, they can operate independent of an operatingsystem or any other unsecure system that would enable an intruder togain access to the authentication information before it has beengenerated and encrypted.

The embodiments of the present are directed to bringing the physicalcomponents closer together, and then teaching how to preventinterference between the components.

FIG. 2A is a cut-away profile that shows the physical components of afirst embodiment of the present invention. In this first embodiment, asystem is shown having touch, display and NFC technology. Specifically,a touch sensor 40 is shown disposed on top of a display screen 42. Thisfigure is directed to showing the stacking or stack-up arrangement ofthe various components, and not specific size relationships. A first NFCantenna 44 is shown disposed under the touch sensor 40, and a second NFCantenna 46 is shown disposed underneath the display screen 42.

FIG. 2A shows that the components are discrete, and do not share anyphysical components such as electrodes. The size of the first NFCantenna 44 should be understood as being smaller relative to the size ofthe second NFC antenna 46.

The relevance of the first embodiment may not be immediately clear. Forexample, the purpose in making the different sizes of NFC antennas isbecause of several factors. The first factor is that the first NFCantenna 44 is a receiving antenna. The receiving antenna may be smallerbecause it is a higher component in the stack-up of the system and isnot being covered by other high attenuating component or components thatgenerate electrical or magnetic interference. Another reason for thesmaller size may be because of NFC specifications that provide forspecific power and size limitations regarding the operating volume ofNFC technology.

Another reason for making a smaller receiving antenna may be to limitthe reach of the communication signals that it can receive. Thislimiting aspect has a practical reason for implementation. For example,smart cards may now include both a magnetic strip and an NFC antenna. Ifa user wants to swipe the magnetic strip and not perform a transactionusing the NFC antenna in the smart card, it is important to limit theability to communicate with the first NFC antenna 44. Thus, the firstNFC antenna 44 may be implemented right under the center of the touchsensor 40 or on a side of the touch sensor that is farthest from amagnetic strip reader.

FIG. 2B shows that in an alternative embodiment, the first NFC antenna44 is disposed on top of the touch sensor instead of underneath it. Thisdesign may operate if the touch sensor 40 is able to compensate for theinterference that may be caused by the first NFC antenna 44.

FIG. 3 is provided to illustrate another aspect of the invention in adifferent embodiment. In this embodiment, a plurality of first NFCantennas 44 that receive signals are disposed just underneath the touchsensor 40. The receiving range of the first NFC antennas 44 isintentionally limited so that the first NFC antennas can be directed tospecific applications, or provide other functions as desired. Forexample, a plurality of limited first NFC antennas 44 may actuallyextend a receiving range of the NFC technology by using multiple smallerNFC antennas. Another function of the small first NFC antennas 44 may beto provide the ability to read small NFC tags or cards.

The other components of the system of FIG. 2 include the touch sensor40. The touch sensor 40 may be implemented as a discrete and standalonedevice, or it may be integrated with the other components. For example,the XY electrode grid of the touch sensor 40 may be all or part of theelectrodes that are used as part of the display screen 42. Theelectrodes may also be shared by the touch sensor 40, the display screen42 and the second NFC antenna 46. The electrodes may also only be sharedby the touch sensor 40 and the second NFC antenna 46. By sharing theelectrodes, fewer electrodes are required to implement the system.

FIG. 4 is a cut-away profile view showing the touch sensor 40 and thesecond NFC antenna 46 sharing electrodes.

FIG. 5 is a cut-away profile view showing the touch sensor 40 and thedisplay screen 42 sharing electrodes.

FIG. 6 is a cut-away profile view showing the touch sensor 40, thedisplay screen 42 and the second NFC antenna 46 sharing electrodes.

When electrodes are shared, it is necessary to prevent interferencebetween the components that are sharing them. Thus, in anotherembodiment of the present invention, a clocking oscillator used in thetouch sensor 40 may also be used as the clocking oscillator for thefirst and second NFC antennas 44, 46 and the display screen 42. The useof a common clocking oscillator signal may provide double-rate samplingbetween the touch sensor 40, the display screen 42 and the first andsecond NFC antennas 44, 46, thereby preventing the unwanted signals fromappearing on the any of the components. Double-rate sampling may form anotch filter at the fundamental carrier frequency of the second NFCantenna 46. This method of sampling may provide an excellent method offiltering because there is perfect synchronization between the touchsensor 40 and the second NFC antenna 46.

It may also be possible to coordinate or synchronize operation of thedisplay with the other components. The present invention teaches how itmay be possible to minimize cross-talk between the components of thepresent invention.

Regarding filtering, it should also be understood that anotherembodiment of the present invention is directed to the use of filteringcomponents disposed in series with the electrodes of the touch sensor40. These filtering components may be used to create notch filters orband-pass filters. The touch sensor 40 may operate in a range that isless than 1 MHz, and the NFC antennas may operate near the 13 MHZ range.Accordingly, the filters may be used to prevent interference between theNFC antennas and the touch sensor.

In one embodiment of the present invention, a capacitor may be placed oneach electrode of the touch sensor 40, between the electrode and ground,to thereby shunt unwanted signal from the transmitting NFC antenna 46.

It should also be understood that the present invention is directed tosimultaneous operation of the components of the system, as well as theability to enable operation of a single component at a time.Accordingly, another embodiment of the present invention is directed todetection by the touch sensor 40 of activation of the second NFC antenna46. This detection of activation of the second NFC antenna 46 may beaccomplished by sampling of a signal from the second NFC antenna.Detection may be accomplished, for example, by connecting a GPIO inputto sensing circuitry of the touch sensor 40. The GPIO input may be anelectrode that is placed near to the second NFC antenna 46. The touchsensor 40 may deactivate itself for a period of time or for as long asthe second NFC antenna 46 is transmitting.

Simultaneous operation of the touch sensor 40 and the second NFC antenna46 may be accomplished by superimposing touch sensor drive signals withsignals on the second NFC antenna through the use of summing operationalamplifiers, an RF splitter or combiner, or other similar means asunderstood by those skilled in the art.

In an alternative embodiment, it may be a function of the presentinvention for the circuitry of the second NFC antenna 46 to detect whenthe circuitry of the touch sensor 40 is activated. The second NFCantenna 46 may deactivate itself for a period of time or for as long asthe touch sensor 40 is sensing.

It may be desirable for the function of the touch sensor 40 to havepreference or priority over the function of the second NFC antenna 46,or vice versa. Therefore, it is considered to be an aspect of thepresent invention to enable one of the devices to have priority overanother device of the system. Having one component have priority overanother is especially desirable when physical structures such aselectrodes may be shared.

In another aspect of the invention, it may be desirable to perform anaction that forces recognition of the touch sensor 40 or of the NFCantennas 44, 46. For example, a unique gesture or a touch zone on thetouch sensor 40 may activate either component.

Turning to another component of the system, the display screen 42 may beimplemented using any appropriate display screen technology. The displayscreen 42 may be implemented as any technology that is compatible withstand-alone or shared operation of the touch sensor 40 and the NFCantennas 44, 46. For example, the display screen 42 may be implemented,but should not be considered limited to, using display technology suchas liquid crystal display (LCD), a light emitting diode (LED) display,and organic light emitting diode (OLED) display technology.

Another aspect of the invention is the relative sizes of the first NFCantenna 44 and the second NFC antenna 46. There may be fewer or nolimitations or operating standards regarding operation of a transmittingNFC antenna. Accordingly, a larger NFC antenna may be disposedunderneath all the other components of the present invention. Because itmay be underneath all of the other components, the system may compensatefor the extra material that a signal must pass through by making thetransmitting NFC antenna larger than the receiving NFC antenna. Thetransmitting NFC antenna may also have the capability of being drivenhard in order to drive the signal through the other components. Thelarger transmitting NFC antenna 46 may thus direct a large signalthrough the components that may be above it and in the direction of areceiving NFC card or tag. Thus, the second NFC antenna 46 is shown asbeing underneath the display screen 42, the touch sensor 40 and thesmaller first NFC antenna 44 in FIG. 2.

Whereas it is preferable to use a low impedance antenna for the secondNFC antenna 46, it is possible to use a low or a high impedance antennafor the first NFC antenna. Electrodes manufactured using indium tinoxide (ITO) may operate well for a high impedance antenna. ITOelectrodes may be disposed on top of a display screen 42 and under atouch sensor 40, and may have the advantage of causing minimalinterference with the visual clarity of the display screen.

Placing a low impedance transmitting NFC antenna around the perimeter ofor below the touch sensor 40 and placing a high impedance receiving NFCantenna below or within the touch sensor may allow the active volume ofthe NFC antennas to be designed to meet industry standards or to havebetter control of a receiving position. The first NFC antenna 44 iscoupled to a high input impedance input circuit of antenna circuitrythat may process received signals, and the second NFC antenna 46 iscoupled to a low output impedance driver circuit of the antennacircuitry that may generate and transmit signals.

Another aspect of the present invention is directed towards minimizinginterference between the components of the system. Reducing interferencemay be useful because of electrical and/or magnetic fields generated bythe components of the present invention. For example, the relativelyhigh voltages used by the NFC antennas 44, 46 may be substantiallygreater than the voltages on the electrodes of the touch sensor 40.

The present invention may provide different methods for reducinginterference between components. For example, in another embodiment ofthe present invention, interference may be reduced using balanced driveelectrode patterns. Balanced drive electrode patterns are used tominimize the coupling of touch sensor 40 voltages onto the NFC antennas44, 46. Balanced drive electrode patterns may also provide additionalmeasurement headroom to the electronics of the touch sensor 40 tothereby compensate for interference by the second NFC antenna 46.

In another embodiment of the present invention, interference may bereduced by using symmetrical routing patterns for electrodes. Electricfield interference created by the voltages placed on the second NFCantenna 46 may be canceled using symmetrical routing patterns such thatthe net voltage coupled onto any sense electrode of the touch sensor 40is minimized. Similarly the magnetic field interference created by thetransmission current in the second NFC antenna 46 may be canceled byusing symmetrical electrode routing patterns such that the net currentinjected into any touch sensor 40 electrode pin is minimized.

In another embodiment of the present invention, a shielding ring may bedisposed between the electrodes of the touch sensor 40 and the secondNFC antenna 46 in order to suppress the electric field created by thesecond NFC antenna. It may be beneficial for the second NFC antenna 46to apply a differential voltage to the shielding ring to help cancel theelectric potential appearing on the second NFC antenna.

Shielding is another method for preventing interference betweencomponents of the system. For shielding purposes in the prior art, itwas often helpful to insert a ground plane behind the electrode grid ofa touch sensor to thereby prevent interaction with touchpad sensorcircuitry that is placed behind an XY electrode grid, such as onopposites sides of a substrate for the XY electrode grid. Such ashielding ground plane would prevent interaction with an LCD if thetouchpad were to be disposed in front of the LCD.

However, this type of ground plane as used in the prior art may allowfor eddy currents to be generated within it as a result of activation ofthe NFC antenna, resulting in loss of magnetic field to an NFC smartcard. Accordingly, it is another embodiment of the present invention toprovide a method of preventing creation of eddy currents in a shieldingground plane.

FIG. 7 is provided to show one method of preventing eddy currents in ashielding ground plane. FIG. 7 is a top view of an embodiment showingtwo layers 50 and 52 of a touch sensor. Preventing eddy currents may beaccomplished by making cuts within the electrodes of the ground planewhile maintaining the suppression of electric field potential. The cutsseparate the electrodes into smaller and discrete electrodes that mayminimize the creation of eddy currents. When making the cuts in theground plane electrodes, it is important that the cuts may be made sothat no closed loop is formed, except to form a conductive path that issuitable to form an NFC antenna if that is needed. Accordingly, anydesign may be used for the electrodes of a ground plane thataccomplishes the purpose of minimizing the creation of eddy currents andwhich does not create closed loops.

FIG. 8 is a top view of an embodiment that shows a ground plane that maybe used with the touch sensor of FIG. 7. Note that when the two layers54 and 56 of the ground plane are superimposed over each other, they areinterdigitated and will provide a complete shield relative to bothmagnetic and electric fields.

FIG. 9 is a top view of another embodiment of the present invention.This figure shows a ground plane implemented on the same substrate as anNFC antenna. The NFC antenna 60 is shown in the middle of the substrate,surrounded by a “split donut” ground ring 62 that is shielding the NFCantenna.

Another purpose of creating the cuts in the electrodes of the groundplane, other than minimizing wasted current from the magnetic fields, isto maximize shielding for the electric fields.

The present invention has described the shared use of electrodes betweenthe components of the present invention. In another embodiment of thepresent invention, a ground plane may be shared with the transmittingNFC antenna.

In another embodiment of the present invention, electrodes of the touchsensor and the NFC antennas may be interleaved on a same substrate.

FIG. 10 illustrates another aspect of the present invention that isdirected to the use of a directional coupler. A directional coupler maybe used to increase the sensitivity of an NFC antenna. For example, thismay be useful when the NFC antenna disposed under the touch sensor 40,the display screen 42, or both the touch sensor and the display screen,might be used to receive NFC signals as well as to transmit NFC signals.Accordingly, a directional coupler may be used to increase a range orsensitivity of the single transmitting and receiving NFC antenna. In oneembodiment shown in FIG. 10, the stack-up is comprised of a touch sensor40, a display screen 42, and an NFC antenna 80 that is for bothtransmitting and receiving NFC signals. The touch sensor 40, the displayscreen 42 and the NFC antenna 80 may also share physical structures suchas electrodes.

In another embodiment of the present invention, in order to reduceinterference from electrical and magnetic fields, it may be possible tocompress the fields being generated by the components of the system.Disposing ferrite on or near substrates of the components may compressthe fields. As a practical matter, ferrite might be suspended in siliconor other material, and then the ferrite suspended in the silicon may bedisposed on the substrates. Ferrite may also be disposed on thesubstrate directly in a ring or other suitable structure.

FIG. 11 is provided as another embodiment of the present invention. In amodification of the embodiment shown in FIG. 2, FIG. 11 shows that atleast one additional substrate 70 may be disposed between the touchsensor 40 and the second NFC antenna 46. The at least one substrate mayinclude conductive surfaces 72. The conductive surfaces 72 may becoupled together at a common point. The purpose of the conductivesurfaces is to suppress interference that may be caused by electric andmagnetic fields generated by the second NFC antenna 46.

It is to be understood that the above-described arrangements are onlyillustrative of the application of the principles of the presentinvention. Numerous modifications and alternative arrangements may bedevised by those skilled in the art without departing from the spiritand scope of the present invention. The appended claims are intended tocover such modifications and arrangements.

What is claimed is: 1.-39. (canceled)
 40. A system that integrates atouch sensor and near field communication antenna technology to providecommunications in a touch sensitive portable electronic appliance, saidsystem comprising: a display screen; a touch sensor having a pluralityof sensor electrodes disposed on top of the display screen to therebycreate a touchscreen; a transmitting near field communication antennathat shares the plurality of sensor electrodes for transmitting a signalthrough the touchscreen, and a receiving near field communicationantenna disposed under or inside the touchscreen for receiving a signal,wherein the receiving near field communication antenna is smaller thanthe transmitting near field communication antenna.
 41. (canceled)
 42. Asystem that integrates a touch sensor and near field communicationantenna technology to provide communications in a touch sensitiveportable electronic appliance, said system comprising: a display screen;a touch sensor having a plurality of sensor electrodes disposed underthe display screen to thereby create a touchscreen; a transmitting nearfield communication antenna that shares the plurality of sensorelectrodes for transmitting a signal through the touchscreen, andreceiving near field communication antenna disposed under or inside ofthe touchscreen for receiving a signal, wherein the receiving near fieldcommunication antenna is smaller than the transmitting near fieldcommunication antenna.
 43. (canceled)